High speed matrix printer



Feb. 22, 1966 c. J. FITCH ETAL 3,236,351

HIGH SPEED MATRIX PRINTER Filed Dec. 5, 1961 6 Sheets-Sheet 1 I/VVENTORS CLYDE J FITCH FRED SALTZ By AA ATTORNEY Feb. 22, 1966 c. J. FITCH ETAL HIGH SPEED MATRIX PRINTER 6 Sheets-Sheet 2 Filed Dec.

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HIGH SPEED MATRIX PRINTER Filed Dec. 5, 1961 6 Sheets-Sheet 5 T M 9 0 0 02200 22 QM Feb. 22, 1966 c. J. FITCH ETAL 3,236,351

HIGH SPEED MATRIX PRINTER Filed Dec. 5. 1961 6 Sheets-Sheet 4 FIG. 4

T0 CONTROL CIRCUIT FIG. 5

Feb. 22, 1966 c. J. FITCH ETAL 3,236,351

HIGH SPEED MATRIX PRINTER Filed Dec. 5, 1961 6 Sheets-Sheet 5 HUN FIG. 7

Feb. 22, 1966 c. J. FITCH ETAL 3,236,351

HIGH SPEEDVMATRIX PRINTER Filed Dec. 5, 1961 6 Sheets-Sheet 6 United States Patent Office 3,236,351 Patented Feb. 22, 1966 3,236,351 HIGH SPEED MATRIX PRINTER Clyde J. Fitch, Endicott, and Fred Saltz, Blnghamton,

N.Y., assignors to International Business Machines Corporation, New York, N.Y., a corporation of New York Filed Dec. 5, 1961, Ser. No. 157,187 13 Claims. (Cl. 197-1) This invention relates to high-speed printing apparatus and particularly to a printing machine which prints characters in a dot pattern from a matrix of identical print elements such as wires or the like.

While not necessarily limited thereto, the present invention relates to a print apparatus having utility as an output printer for equipment such as computers or the like utilized in data handling.

Printing machines are known in which the outlines of characters are formed by printing the appropriate dots of a iii-dimensional dot matrix having the same general size as the characters to be printed. One version of such a machine, sometimes called a wire printer, employs a matrix of individually operable dot printing wire elements or the like which are projected in combination simultaneously against a platen to effect printing of the whole character on an interposed print medium. For printing a complete line of data, means is provided for effecting a relative longitudinal motion between the print matrix and the platen (and print medium) so that different characters are printed in series at successive positions along the print line. In previous devices serial (or series parallel) printing was performed incrementally, i.e., the print head or the paper carriage is moved in a succession of step-like motions longitudinally such that the print mechanism is aligned with every or certain ones of the print positions at which data is recorded. A characteristic of incremental motion is that motion is interrupted so that one of the members moves in steps along a print line. It can be appreciated that if printing with incremental motion is to be performed at high rates of speed, the moving parts must be accelerated from rest, advanced, brought to rest rapidly in short intervals of time. In addition, it is essential that the acceleration, advance, deceleration and stopping be performed at a high repetition rate.

Previous devices which print with an incremental motion were often limited devices. This was in part attributed to the fact that the moving elements were massive so that acceleration, deceleration, and stopping was a problem. Devices designed to move a print head incrementally along a print line of increased speeds frequently were unduly complex in structure and function. Uniformity and precise registration of the print head was generally unobtainable on a consistent basis at high speeds. As a result, print quality was not always satisfactory and reliability was frequently lacking.

It is the general object of the present invention to pro vide an improved print apparatus in which incremental motion is obtained at high rates of speed without sacrificing print quality.

It is also an object to provide an improved print apparatus in which high speed incremental relative motion of a print element and a print medium is attainable with means having relatively simple constructional characteristics and reliability, and which is capable of producing uniformly good quality printing output.

It is a further object of the present invention to provide an improved wire printer apparatus having an improved means for moving a wire print head incrementally for printing in a serial manner.

It is a still further object of the present invention to provide an improved printing apparatus capable of being operated in an asynchronous manner.

The preceding and other objects are attained in accordance with the practice of the present invention by providing a print apparatus freely movable in forward and reverse directions. Incremental motion is imparted to the print mechanism by a drive means which functions to perform both as an advancing mechanism and a stopping device. This is accomplished by having a drive means operable in both forward and reverse directions in combination with a motion detection device adapted to reverse the drive means after a predetermined increment advance of the print mechanism by the drive means in the forward direction. Specifically, a motive means operable in both forward and reverse directions is utilized to advance a print mechanism mounted on a transport device when operating in the forward direction and to stop the print mechanism after a predetermined forward advance by operating in the reverse direction in response to a means which detects a predetermined advance of the print mechanism. In the preferred form of the invention, the motive means comprises first and second motive devices individually operable in opposite directions and the forward advance is obtained by connecting the transport member to the first motive device for moving it in the forward direction and the stopping action is obtained by connecting the transport member to the second motive device operating in the reverse direction.

In the preferred embodiment of the invention, the first and second motive means are clutch members and the transport member includes a flexible band selectively coupleable to said clutch members. More specifically the clutch members are electro-adhesive rotor members which are continuously rotatable and the clutch band is electrically conductive 0s as to he coupleable by electrostatic adhesion to the surface of the rotor members. A control means includes means for supplying an advance electric pulse to the first rotor member so that the transport band is coupled thereto. After the print head has advanced a predetermined increment along the print line, the advance electric pulse to the first rotor is discontinued and a stop electric pulse is applied to the second rotor. The transport band is thus electrostatically de-coupled from the first rotor and electrostatically coupled to the second drive rotor to effect an application of a deceleration and stop force.

It will be appreciated that rapid starting and stopping of the transport member can be attained utilizing a pair of oppositely moving drive means. By using a pair of continuously rotating electrostatic clutch rotors and a flexible clutch band for supporting the print head, a relatively simple construction is provided for an incremental motion device. In addition, the rotor members can have high dynamic inertia while the transport member and print head are relatively low inertia devices thereby making the starting and stopping of the incremental motion of short time duration so that high printing speeds are attainable.

Also by using electrostatic clutches for the incrementing means, which are voltage controlled and fast in response, a high repetition rate is easily achieved. In addition, precision control over the location of the print element at successive positions along a print line is obtained in accordance with another feature of this invention by providing a means which senses the length of travel of the print element and operates the brake clutch to bring the print head to a stop. In the preferred form the motion sensing device comprises an increment track member having increment indicia thereon and an increment detector means, either of which is made movable relative to the other with the print element. In the preferred embodiment, the increment track takes the form of a plurality of uniformly spaced marks formed on or in the transport band member and the mark sensing device is supported at a fixed position relative to the tape. A sense indication from the mark sensing device is used to de'couple the band from the first rotor and connect it to the second rotor.

To further increase the speed at which printing can occur serially, the print apparatus of the present invention takes the form of a wire printer in which a plurality of individually movable wires are formed at one end into a bundle or matrix and the other ends of the wires forming the matrix are individually attached to the clutch band transport member. To obtain vertical stability, the clutch band and print element assembly is formed to ride in a stationary track formed preferably from a pair of track members shaped to provide a track recess for receiving a guide member attached to the print head. Friction elements carried by the guide member engage the track members to give the transport assembly a measure of longitudinal stability without limiting the free mobility for movement of the transport member by the drive members in either direction. The high speed operation of the wire print elements is obtained by a wire drive device comprising an electro-adhes'ive clutch rotor. For this purpose, the ends of the wire print elements remote from the printing end are attached to individual conductive bands which are preferably arranged in a parallel array in contact with at least a portion of the periphery of the electro-adhesive print drive rotor. Electric pulses to selective ones of the conductive print wire drive bands in timed relation with .the incremental operation of the print element produce a print impression of selective mosaic data impressions in successive operations for printing a line of data at plural positions along a print line.

Thus, it will be seen that a new and improved high speed serial wire printer mechanism has been provided. It will also be seen that an improved high speed printer apparatus has been provided which is capable of producing uniformly good quality printing. It will be further appreciated that a print apparatus has been provided which is asynchronously operable, i.e., the printer is always in a standby condition and will print immediately on receipt of an input signal.

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of a preferred embodiment of the invention, as illustrated in the accompanying drawings.

In the drawings:

FIG. 1 is a schematic presentation in perspective form of a serial printer embodying the principles of the present invention.

FIG. 2 is a detailed plan view looking from .above of a specific mechanism incorporating the mechanical elements forming the printing and transport devices of the present invention.

FIG. 3 is a rear elevation of the device of FIG. 2 with the platen removed.

FIG. 4 is a detail from FIG. 3 showing in enlargement the print head and associated transport assembly as seen from the point of view of the platen.

FIG. 5 is a detail from FIG. 3 show-ing a device for sensing the ind-icia forming the increment track on the electrostatic clutch band of the device of FIG. 2.

7 FIG. 6 is a side elevation in partial section of the electrostatic clutch mechanism used for driving the print wire elements.

FIG. 7 is a side elevation in section from the right of FIG. 2 showing details of the transport mechanism and assembly of FIG. 2.

FIG. 8 is a circuit diagram illustrating an embodiment of a control for operating the mechanisms of FIGS. 1-7 as a serial incremental printer.

Referring to the drawings, the printer apparatus of FIG. 1 comprises a print unit for printing characters one at a time at successive positions along a print line. A print medium 10 such as a continuous forms paper document is moved past the print line by any conventional means including a platen 11, rotatably driven by controls 12 connected to shaft 13. The mechanism for positioning and advancing the paper may take the form of any of the mechanisms which are known to the art having the capability of advancing the paper one or more line spaces at a time in coordination with the printing portion of the cycle of operation. The printing of characters on the paper 10 is in the preferred embodiment of the present invention obtained from a printing unit having a plurality of wires 14 grouped together at one end to form a matrix print head 15. The wires 14 are guided in tubes in the usual Bowden manner. In accordance with the principles known in the printing art, each of the wires 14 is selectively individually movable within its .tube, in combination with other wires to form various characters. In accordance with the present invention, the selective operation of the wires 14 is under the control of a continuously rotating electro-adhe'sive rotor 16 driven at constant speed by suitable drive means such as motor .17. The individual wire elements 14 are selectively coupled to the rotor member 16 in a manner to be more fully described hereinafter by a print head motion and character selector control 18 adapted to receive coded electrical input signals from a computer, a transmission line, a data card, magnetic tape or the like. Character imprints are formed on the print medium 10 when the individual wires 14 are driven by the rotor 16 forward from the matrix of print head 15 to strike ribbon 19 against paper 10 in the usual manner.

In accordance with the practice of this invention, the print head 15 is moved incrementally along the print line and characters formed by the matrix of wires of print head 15 are placed serially at successive positions along the print line. The mechanism for transporting the print head 15 (shown schematically in FIG. 1) comprises a pair of spaced apart, continuously rotating electrostatic clutch rotors 20 and 21 selectively connectable to a flexible conductive transport band 22 to which print head 15 is attached in a suitable manner. For the purpose of advancing the print head 15 as shown in FIG. 1, rotor 21 is continuously rotatable in a clockwise direction. For selective stop-ping the forward motion of print head 15, rotor 20 is continuously rotatable in a counterclockwise direction. The transport 22 is made of an electircally conductive material such as steel, so that electric voltage applied to rotors 20 and 21 causes the band 22 to be electrostati-cally attracted thereto.

A more detailed assembly of one form of the print unit of FIG. 1 may be seen by referring to FIGS. 2-7. As shown in those figures, a vertical support plate 23 secured to a horizontal base member 24 supports the electro-adhesive drive rotors 20 and 21 in fixed spacedapart relation. Platen 11, which may be mounted on base member 24, is located on one side of support plate 23 with its axis of rotation parallel thereto. Drive rotor 20 is mounted on plate member 23 by a shaft 25 rotatably journalled thereto. A drive connection of shaft 25 to a constant speed motor (not shown) is provided by means such as pulley 26. Rotor member 21 is mounted on support plate 23 on the right end of platen 11 (as seen in FIG. 2) by shaft 27, which is journalled to plate member 23. A drive connection for shaft 27 to a constant speed motor (not shown) is provided by suitable means such as pulley 28.

The arrangement of the transport band 22 for drive connection to the rotor members 20 and 21 may be seen more clearly in FIG. 3. As shown there, transport band 22 is formed in a continuous loop which lies in a vertical plane substantially parallel to the support plate 23. The upper portion of the loop passes over the rotor members 20 and '21 so that it is physically in contact with at least a portion of the peripheral surfaces thereof. A pair of loop guide members 29 and 30 which are suitably mounted on support plate 23 are located proximate and below rotor members 20 and 21 respectively. Loop guide members 29 and 30 direct band member 22 vertically downward in a curved path to the lower section of the loop where guide pegs 31 are arranged in a row extending across the lower portion of the loop between the rotors 20 and 21. The guide pegs 31 are arranged in a curvilinear path in order to dampen undesirable mechanical vibration of the transport band 22. The band 22 has a resilient kink in it, 22a, to pro vide uniform tension and compensate for any eccentricities of the rotors 20 and 21.

The print head is attached to the transport band 22 in the upper straight section of the loop intermediate rotors and 21. Also, a stationary guide track is provided for the straight portion of the loop of band member 22 which serves to guide the print head 15 in its movement along the print line in the section between the rotor 20 and 21. In the preferred embodiment, the print head is part of an assembly such that it may be attached to the band member '22 and at the same time be guided by the transport guide track.

As best seen in FIGS. 4 and 7, the print head 15 comprises a bundle of wires 14 held near one end in a matrix pattern by a print head block 32. The print head block 32, in turn, is mounted in a print head carriage assembly adapted to carry the print head 15, to be attached to transport band 22, and to co-act with the guide track to guide print head 15 in a straight line along the print line.

The print head carriage assembly comprises a pair of attachment blocks 33 and 34 and a guide block 35 secured together in superimposed relation by suitable means such as screws 36. The upper and intermediate attachment blocks 33 and 34 are shaped on their common surface to form a recess adapted to receive print head block 32 while the intermediate blocks 34 and the low blocks 35 are designed to attach the carriage assembly to the band member 22. In this regard, the attachment is facilitated by arranging the loose ends of the band member 22 to overlap between the guide block 35 and the intermediate attachment block 34 so that the dual function of loop continuity and print head attachment is achieved in a single assembly.

The transport guide track (see FIGS. 3 and 7) for controlling the longitudinal motion of the print head 15 may take various forms but in one preferred form comprises a pair of track members 37 and 38 secured in face, relation to support plate 23 intermediate the rotor members 20 and 21. A cooperative guiding connection is obtained by shaping the meeting surfaces of the track members 37 and 38 so as to provide a pair of recesses 39 and 40. Recess 39 extends horizontally across the upper straight portion of the loop of band member 22 and is adapted to receive the same for movement therethrough. Recess 40 (as seen in FIG. 7) which is located below the recess 39, is attached to receive the guide block 35. To assure that the carriage assembly has stability in a vertical direction, the guide block 35 is preferably larger in cross section than the attachment block 34. Thus, when guide block 35 is in recess 40, the upper shoulders thereof engage the upper horizontal surfaces of recess 40 and vertical motion is minimized. To obtain a measure of longitudinal stability without restricting the longitudinal motion of the band member 22 and carriage assembly, the guide block 35 is provided with friction elements adapted to engage the inner surfaces of track members 37 and 38 in the recess 40. Suitable friction elements as shown in FIG. 7 take the form of friction pads 41 and 42 within one or more recesses 43 in the sides of guide block 35. A compression spring 44 between the friction pads 41 and 42 supplies pressure to the friction pads 41 to maintain them in contact with the inner side surfaces of the track members 37 and 38.

As previously stated, the printing of characters on print medium 10 is effected by selectively driving various combinations of print Wires 14 so that the ends thereof strike print ribbon 19 against the paper document 10. The mechanism for driving wires 14 may be more clearly understood by reference to FIG. 6. As shown therein, each of the print wires 14 at their ends remote from the ends formed into a matrix of print head 15 is connected to print bar 50 which is slidably mounted on spaced front and rear horizontal support bars 51 and 52 respectively. Lugs 53 and 54 on print bar 50 co-act with the support bars 51 and 52 to limit the forward and return movement of the print bar 50. A leaf spring 55 attached to block member 56 bears against the front end of lug 54 to bias print bar 50 to its retracted position. To permit the bias of spring 55 to be adjusted to control and make uniform the retraction forces on the various print bars 50, block member 56 is made slidably adjustable on rear support bar 51 by means such as rotatable screw 57 rotatably attached to block 56 and nut 58 fixedly attached to support bar 51.

For driving each of the print bars 50, an electrostatic clutch rotor 16 having a shaft 61 is rotatably mounted in a suitable manner, preferably on base member 24, below support bars 51 and 52. The connection of the print bar 50 to rotor 16, which is continuously rotated by motor means (not shown), is effected through a print Wire clutch band 62 having one end insulatingly connected to the rear end of the print bar 50 with its opposite end anchored to a stationary peg 63 secured to the base member 24. The clutch bar 62, which is arranged to have a portion of its surface in contact with the periphery of clutch rotor 16 may be provided with a slack take up bend 64. Of course, it is understood that a separate clutch band 62 is connected to each of the various print bars 50 in a similar manner so that there is the necessary mechanical connection between the rotor and each of the print bars as described.

Electrostatic clutches suitable for driving print wires 14 are known to the art. Briefly, the rotor 16 of such clutches is provided with a peripheral surface formed from a layer 65 of electro-adhesive material such as semi conductive material. One type of such material is a mixture including rubber, phenolic, asbestos, and carbon as more fully described in Patent No. 2,923,390, issued February 2, 1960. Layer 65 is superimposed on a base of conductive material which is connectable to an electric circuit with the print wire clutch band 62. Such connections are well known in the art and may include a connection through the shaft 61. Clutch band 62 is a conductor material, preferably spring steel, and has its under surface in continuous contact with the outer surface of semi-conductive layer 65. The electrical arrangement of clutch band 62 and rotor 16 is such that voltage may be applied across the band 62 and layer so that electro-adhesion is obtained while the voltage is applied causing the print wire band 62 to be mechanically driven by rotor 16 as it rotates on shaft 61.

The effectiveness of the electro-adhesive attachment of the rotor to band 62 is improved by applying a liquid, e.g., Dow Corning DC200 silicone fluid having a viscosity preferably between 1000 and 10,000 centistockes, to the surface of the semi-conductive layer 65. For that purpose, an applicator roll 66 is rotatably mounted through shaft 67 so that liquid absorbing fibers 68 of the peripheral surface thereof continuously wipe liquid onto layer 65 of clutch rotor 16. Liquid is supplied to the fibers 68 of roll 66 from a reservoir tank 69 through wick 70, which is in contact with a roller 71 located to be wiped by the fiber 68. Suitable motor drive is provided to rotate applicator roll 66 and roller 71 at a speed proportional to the speed of rotation of clutch rotor 16 so that liquid 72 is applied uniformly in controlled amounts onto the surface of layer 65.

In the preferred form of this invention, the rotors 20 and 21, which transport the print head 15 incrementally along the print line, are also electrostatic clutches of the type shown in FIG. 6. Their construction, therefore, could be substantially the same as that described for rotor 16 or may take the form of one of the other electrostatic clutch devices known in the art. Where the rotors 20 and 21 are of the type shown in FIG. 6, means for applying a liquid to the electro-adhesive layer may also be provided. As seen in FIG. 2, a rotary liquid applicator for rotor 20 is mounted on a shaft 76 rotatably journalled to vertical support plate 23. A drive motor 77 is mounted on a support plate 23 by bracket 78. The drive connection of motor 77 to shaft 76 is formed by a pulley wheel 79 attached to motor shaft 80 and connected by a belt 81 to a pulley wheel 82 on a gear train shaft 83 rotatably journalled to the frame 23 and bearing a drive gear 84 in engagement with a gear 85 on shaft 76.

The incremental drive rotor 21 is similarly provided with a liquid applicator roll 86 supported on a shaft 87 rotatably journalled to support plate 23. A drive motor 88 is mounted on support plate 23 by motor bracket 89. The drive connection of motor 88 to shaft 87 is formed by a pulley wheel 90 attached to motor shaft 91 and connected by a belt 92 to a pulley wheel 93 attached to gear train shaft 94 which is rotatably journalled to support 23 and carries a gear 95 engaging a drive gear 96 on shaft 87.

In accordance with this invention, the print mechanism heretofore described operates substantially as follows. The print head 15 is advanced incrementally along the print line parallel to platen 11. The incremental advance of the print head 15 is obtained by applying voltage to rotor member 21 so that transport band 22 becomes elcctrostatically engaged to rotor 21 which is rotating in a clockwise direction. the length of advance of the print head 15 consequently the length of advance of an increment is dependent upon the spacing of the holes 100 on the transport band 22. As previously stated supra, means is provided for sensing the distance that the print head 15 is allowed to advance. When the advance has been made the predetermined amount, e.g., one print position, the voltage on rotor 21 is discontinued. In accordance with this invention, not only is the voltage discontinued on the rotor 21, but a predetermined short voltage pulse is applied to rotor 20 which rotating continuously in a counterclockwise direction is electrostatically coupled to the band 22 to stop print head 15 at a desired print position. For the purpose of sensing the printing or stopping positions that control the print head 15, there is provided a series of uniformly spaced track increment indicia in the form of holes 100 in band member 22. A mark sensing device 101 for detecting the presence of the holes 100 is located near the left end of platen 11, where the beginning of print line occurs. The details of a specific type of mark sensing device may be seen more clearly in FIG. 5. A continuous light source 102 is mounted in a housing member 103 which is attached in any suitable manner such as by screws 104 and bracket 105 to vertical support plate 23. Within housing 103 the light source 102 is mounted in a cham her 106 having aperture 107 through which a beam of light can shine onto the upper surface of band member 22. Located on plate 23 below the band member 22 is a light sensitive element 108 such as a photocell which, when receiving light, generates an electric pulse delivered by a conductor 109 to a control circuit to be described hereinafter. As the transport band 22 moves along the print line past the housing 103 of the mark sensing device, the light from light source 102 emanating through aperture passes through successive holes 100 to generate a series of electric pulses to the circuit for controlling the selective alternate connection of rotors 20 and 21 to band member 22. The control of the increment of motion of the band member 22 is therefore very precisely controllable to the degree of precision obtainable by locating the marked holes 100 on the band member 22.

Other increment track means and devices for marking the increments and mark sensing means may, of course, be used as will occur to persons skilled in the art. While the preferred embodiment shows the mark sensing means 101 stationary and the transport 22 movable, the relative motion of these two devices may be interchanged so that the track indicia are stationary and the mark sensing device is movable. However, since the object of the present transport mechanism is to attain rapid acceleration and stopping, the marking of the band 22 with holes 100 as well as making the mark sensing means 101 stationary, are preferred since such practices tend to minimize the mass to be moved by the transport mechanism.

In FIG. 8 a printing system, adapted for recording characters serially at successive positions along a print line is shown. In general data signals are delivered serially from a data source 110 to a print control unit 111, where the signals are converted to a parallel signal output which can be used by a print wire selector device 112 for operating electrostatic clutch rotor 16 to simultaneously drive a plurality of print Wires 14 corresponding to the character designated by the input signal. In addition, print control unit 111, under the control of the data input 110, generates, in timed relation with the receipt and conversion of the code signals, time pulses which are utilized for energizing the rotors 21 and 20, for incrementally advancing the print head 15 and feeding the print medium to the carriage control device 12. In the system described in FIG. 8, the data signal source 110 may be any type of device which generates coded electrical signals in a series of successive voltage pulses or bits and could include a transmission line receiver where the input from the data source is a modulated transmission signal. In such event, the input source 110 could provide means for demodulating the transmission line signal to deliver the data signal in series-bit form. Or the input source 110 may be a computer or data processing device adaptedfor generating a series of bits indicative of data to be recorded. In connection with the specific details of the serial print system to be described for the present invention, a binary code of six bits plus a seventh bit for checking will be the convention. However, it will be understood that other code conventions can be utilized within the concept of the invention.

In print control unit 111, each stage of a multistage timing ring 113 has an output 114 connected through individual gating AND circuits 115 having outputs 116 connected to corresponding stages of a single character register 117. Each stage of register 117 has an output 118 connected through corresponding individual ones of a second group of gating AND circuits 119 having output connections 120 to a decode matrix 121. Multiple outputs 122 equal in number to the number of bits are connected from the decode matrix 121 to corresponding ones of a third group of gating AND circuits 123 having individual outputs connected to the print wire select matrix 112.

An input 125 to the first stage of the timing ring 113 is connected to starting device (not shown) which is part of or under control of the data source 110 and may be a clock circuit of a well-known type. A data signal output 126 from data source 110 is connected to all of the gating AND circuits 115 having connections with the output 114 of the several stages of timing ring 113. Timing ring 113 is preferably the free-running, openended type in which each of the stages is connected to a successive stage so that a start pulse delivered to the first stage starts the ring running so that each stage switches its following stage to deliver signal pulses in successive steps to the gating AND circuits 115 and the running of the triming ring 113 terminates with the switching of the last stage.

The pulsing of the first stage of the timing ring by the start device of data source 110 occurs as the first bit of a data signal is sent to the first group of gating AND circuits 115 and switching of the successive stages of timing ring 113 in accordance with its free running characteristic occurs in synchronism with the generation of the succeeding bits from data source 110. The last stage of timing ring 113 has a second output 127, connected to all the individual AND circuits 119, which gates the pulses from the single character register 117 to the decoder 121. The second output 127, from the last stage of timing ring 113, is connected through a single shot 128 to driver 129 which has an output 130 connected to the third group of AND circuits 123 which are connected to the print wire select device 112.

In accordance with the operation of the print system utilizing the principles of the subject invention, operations pulses from the last stage of timing ring 113 are also utilized to control the advice of print head after printing has occurred at a print position. For this purpose, the output of driver 129 is connected to a single shot 131, which in turn is connected to one side of flip-flop 132, having a first output 133 connected through brush 134 to rotor 21 of the print head transport mechanism. The second side of flip-flop 132 has an input 135 connected from mark-sensing device 101 and an output 136 connected to a single shot 137 having an output 138 connected through brush 139 to rotor of print head transport mechanism.

For controlling the return of print head 15 from the end of the print line to the first print position at the end of the printing of a complete line of data, a pair of limit switches 140 and 141 are provided and are located at opposite ends of a print line adjacent the print head transport mechanism and adapted to be operated by the print head 15 in appropriate limit positions. For that purpose limit switch 140 is connected to the ON side and limit switch 114 is connected to the OFF side switching circuit 142. An output 143 from switching circuit 142 is connected through brush 139 to rotor 20.

Print control unit 111 preferably includes means operable for indicating the end of a line of data where less than a full line has been printed. Such a device may be a variable set counter mechanism set upon instruction from data source 110, or a coded carriage return signal as employed in printing telegraph art. An output from the end of line indicator of print unit 111, shown as part of the decode matrix block 121, is connected to the ON side of the switching circuit 142. A second output 145 from the print control unit 111 may be connected to carriage control 12 and may be integrated on instruction from the data source 110 to initiate carriage operation upon completion of the recording of a line of data.

Briefly the operation of the printer as shown in FIG. 8 is as follows:

A start pulse from data source 110 on lead 125 starts the cycle of timing ring 113. coincidentally with the start pulse on lead 125 the first bit of the coded data is sent on lead 126 to the first inputs of AND circuits 115. If the first bit is a pulse, a coincident pulse from first stage of ring 113 on input 114 will cause a pulse from the corresponding AND circuit 115 to energize lead 116 and switch the first stage of register 117. As the timing ring 113 steps along, the bits of data are applied to gates 115 on lead 126. Whenever pulses from the stages and from line 126 are applied coincidentally to various gates 115, the corresponding stages 117 are switched. As each stage of register 117 is switched, output leads 118 to AND gates 119 are energized. The leads 118 remain energized until timing ring 113 has completed its cycle and the last stage has been switched. When that occurs, lead 127 is energized and those AND gates 119 having coincidentally energized inputs 118 and 127 energize outputs 120 to the decoder 121. In decoder 121, a conversion of the 6- bit code is effected so that certain wires connected to conductive bands 62 are operated. For that purpose various ones of leads 122 corresponding in number to the number of wires necessary to form an imprint of the charac- 10 ter indicated by the code input to decoder 121 are energized. A pulse from driver 129 to the second inputs to AND gates 123 operates to energize various leads 124 in wire selector matrix 112. The fire pulse from driver 129 is derived from SS 128 which in turn uses the pulses from lead 127 which gates the character signal to decoder 121. The pulse from SS 128 is preferably slightly delayed so that the conversion by decoder 121 can occur and suitable leads 112 energized before the fire pulse is pro- I duced.

Upon occurrence of the fire pulse from driver 129, certain print wire bands 62 will have volt-ages applied thereto from selector matrix 112. Wires connected to the bands will operate under force supplied by the rotation of rotor 16 to simultaneously strike a print medium to produce an imprint of the character selected by data source 110.

Upon completion of the print operation, the printer is in condition for a subsequent operation. The second operation occurs when the print head 15 has been advanced to the next print position and a second word is supplied by data source 110 in the manner previously described. Print head advance occurs when the firing pulse from driver 129, after suitable delay at SS 131, switches flip-flop 132 to energize lead 133 and applies a voltage to print head advance rotor 21. Transport band 22 thereupon is electroadhesively coupled to rotor 21 and print head 15 is moved under force supplied by that rotor. Upon advance of band 22, a distance mark 100 is sensed by photocell 101 via a beam from light 102. A pulse is applied to lead 135 which switches flip-fiop 1 32 and de-energizes lead 133. The electroadhesive coupling of band 22 and rotor 21 is thus terminated. In addition to de-energizing lead 133, flip-flop 132 on the pulse from photocell 101 energizes lead 136 to switch SS 137 which energizes lead 138 to pulse rotor 20. Rotor 20 which rotates in a direction opposite rotor 21 engages band 22 and applies a braking action which stops the advance of print head 15. The pulse from SS 137 may be closely controlled so that the duration of braking is very closely determined, thus assuring precise stopping of print head 15. During the advance of print head 15 or shortly thereafter on signal from the print mechanism, for example, data from source 110 and the start pulse in synchronism is again fed to control unit 111 Where the serial to parallel conversion and decoding operations are repeated as previously described. Print head advance then occurs again in the manner described. The cycle of operation is repeated until such time as a complete line of data is printed.

After printing in the last line position occurs, print head 15 is advanced by rotor 21 to engage limit switch 140. A pulse from photocell 101 switches flip-flop 132 to de-energize rotor 21 and energize rotor 20 from SS 137. When limit switch 140 is closed, switch 142 is turned on. This operates to energize rotor 29 from lead 143. Rotor 20 remains energized until print head 15, moving under force applied through transport band 22 from rotor 20, comes into contact with limit switch 141. When contact is made, switch 142 is turned off, lead 143 is de-energized, and band 22 is declutched from rotor 20. Print head 15 then rests in position in preparation for a subsequent printing cycle. Upon advance of print medium, under instruction from carriage control 12, either concurrently with or subsequent to return of print head 15 to print position one, for example upon signal from limit switch 140, the print mechanism is ready for printing a subsequent line of data.

While the invention has been particularly shown and described with reference to a preferred embodiment thereof, it will be understood by those skilled in the art that the foregoing and other changes in form and details may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. In a printer apparatus the combination comprising a print element; means for moving said print element incrementally along a print line relative to a print medium comprising transport means for said print element, said transport means being movable in forward and reverse directions along said print line; drive means for moving said transport means in said forward and reverse directions including motive means operable in forward and reverse drive directions corresponding with said forward and reverse motion directions of said transport means; and incrementing control means for said drive means com-prising means for periodically activating said motive means in said forward drive direction, and means for stopping said transport means following each forward advance thereof by said motive means comprising means for detecting the advance of said transport means a predetermined incremental distance, .and stopping means responsive to said detecting means operable to stop said transport means by deactivating said motive means in said forward drive direction and activating said motive means in said reverse drive direction for a predetermined interval of time after a forward advance whereby said transport means is braked to a stop.

2. In a printer apparatus, the combination in accordance with claim 1 in which said means for detecting said forward advance of said transport means comprises coacting increment control indicia and indicia sensing means, said indicia and indicia sensing means being relatively movable in accordance with the motion of said transport means along said print line, and said stopping means for said transport means includes means responsive to an indication from said indicia sensing means for actuating said motive means in said reverse direction for said predetermined interval of time.

3. In a printer apparatus, the combination in accordance with claim 2 in which said control indicia means are movable with said transport means.

4. In a printer apparatus, the combination in accord- 4O ance with claim 2 in which said transport means comprises a relatively inextensible continuous flexible band member connected to said print element, and said control indicia means comprises sensible distance marks corresponding with incremental distances of said print line formed in said band member.

5. In a printer apparatus, the combination in accordance with claim 1 in which said motive means comprises a first clutch member selectively connectable to said transport means and operable in said forward drive direction, a second clutch menrber selectively connectable to said transport means and operable in said reverse drive direction, and said incrementing control means comp-rises means for periodically connecting said first clutch member to said trans-port means and said means responsive to said forward advance detecting means comprises means for successively disconnecting said first clutch member from said transport means and for connecting said second clutch member in said reverse drive direction to said transport means for said predetermined interval of time.

6. In a printer apparatus the combination in accordance with claim 5 in which said transport means comprises a flexible relatively inextensible band member connected to said print element and said first and second clutch members include rotor members continuously rotatable in said forward and reverse drive directions respectively, and said rotor members are selectively frictionally connectable to said band member.

7. In a printer apparatus in accordance with claim 5 in which said first and second clutch members comprise first and second electro-adhesive rotor members continuously rotatable in said forward and reverse drive directions respectively and said transport means comprises a band member encircling at least a portion of the peripheries of said rotor members, and said incrementing control means comprises means for periodically applying connecting potentials selectively tosaid first rotor member, and said means for stopping said advance of said band member includes means responsive to said detecting means for successively disconnecting said potential applied to said first rotormernber and for applying a connecting potential to said second rotor member for said interval of time.

8. In a printer apparatus, the combination in accordance with claim 1 further comprising means for returning said print element to an initial print position along said print line including means for detecting the arrival of said print element at an end of line location along said print line, said end of line location being a predetermined number of forward increments from said initial print line position, means responsive to said end of line detecting means for activating said motive means in said reverse direction, means for detecting the arrival of said print element at said initial print line position, and means responsive to the indication from said initial print position detecting means for dc-activating said motive means from said reverse direction and for activating said motive means in said forward direction a predetermined interval of time whereby said transport means is stopped at said initial print line position.

9. In a printer apparatus for recording characters or the like serially in a line across a print medium, the combination comprising:

a print mechanism movable in forward and reverse directions across said print medium;

means for advancing said print mechanism in increments across said print medium including drive means operably connected thereto and operable in forward and reverse directions,

means for activating said drive means in said forward direction to advance said print mechanism in said forward direction,

means for stopping the advance of said print mechanism after a predetermined increment of forward movement thereof including means for detecting an increment of forward movement of said print mechanism and means responsive to said detecting means for deactivating said drive means in said forward direction and activating said drive means in said reverse direction for a predetermined time to stop forward increment of the print mechanism.

10. In a printer apparatus for recording characters or the like serially in a line across a print medium, the combination comprising:

a print mechanism;

a trans-port means for said print mechanism movable in forward and reverse directions across said print medium;

means for advancing said transport means in increments across said print medium including drive means operably connected to said transport means and operable in forward and reverse directions,

means for activating said drive means in said forward direction to advance said transport means in said forward direction,

means for stopping the advance of said transport means after a predetermined increment of forward movement thereof including means for detecting an increment of forward movement of said transport means and means responsive to said detecting means for deactivating said drive means in said forward direction and activating said drive means in said reverse direction for a predetermined time to bring the transport means to a stop.

11. In a printer apparatus for recording characters or flexible relatively inextensible electrically conductive the like serially in a line across a print medium, the corn- 13 bination in accordance with claim 10 in which said drive means includes:

first and second motive devices, said motive devices being individually continuously operable in forward and reverse directions respectively,

said transport means being selectively couplable to said first and second motive devices, and

said means for advancing said transport means in increments includes means for selectively alternately coupling said transport means to said first and second motive devices.

12. In a printer apparatus for recording characters or the like serially in a line across a print medium, the combination in accordance with claim 11 in which said means for stopping the advance of said transport means includes:

increment indicia bearing means movable with said transport means,

said indicia bearing means having increment indicia thereon detectable by said detecting means upon movement of said transport means.

13. In a printer apparatus for recording characters or the like serially in a line across a print medium, the combination in accordance with claim 12 in which said transport means includes:

a belt member operably connecting said print mechanism and said drive means and having said increment indicia formed thereon.

References Cited by the Examiner UNITED STATES PATENTS 2,708,020 5/1955 Wookenfnss 197--1 2,773,443 12/1956 Lambert 10l93 2,802,414 8/ 1957 Johnson 10193 2,831,424 4/ 1958 MacDonald 101-93 2,884,852 5/1959 Saltz 10193 2,909,996 10/1959 Fitch 10193 2,911,085 11/1959 Leathers 197-1 2,997,152 8/1961 Dirks 197-1 ,135,195 6/1964 Potter 101-93 ROBERT E. PULFREY, Primary Examiner.

R. A. LEIGHEY, WILLIAM B. PENN, Examiners. 

